Product and process



2,739,078 Patented Mar. 20, 1956 PRODUCT AND PRGCESS No Drawing.Application March 6, 1952,

' Serial No. 275,248

7 Claims. (Cl. Hid- 308) This invention relates to surface-modifiedfinely divided siliceous solids and to their production. It is moreparticularly directed to inorganic siliceous particles having an averagespecific surface area of at least 1 square meter per gram, havingchemically bound to the silicon atoms on the surface of said particlesat least 100 ORO- groups per 100 square millimicrons of surface area ofthe siliceous solid, Where R is a divalent hydrocarbon radical havingfrom 2 to 18 carbon atoms and in which each of the two carbon atomsattached to oxygen is also attached to at least one hydrogen atom.

The method of surface-modifying dense siliceous particles in accordancewith this invention comprises chemically reacting in a hydrocarbonsolvent substrate particles of inorganic siliceous material having anaverage specific surface area of at least 1 square meter per gram with aglycol of formula HOROH where R is a divalent hydrocarbon radical havingfrom 2 to 18 carbon atoms and in which each of the carbon atoms attachedto oxygen is also attached to at least one hydrogen atom.

The products of the invention are a specific kind of siliceoussolids.Some of these products I refer to hereafter as estersils. Estersils aresolids made by chemically reacting hydroxy compounds with certainsupercolloidal siliceous solids. The reaction I have calledesterification and the chemically bound ORO groups resulting therefrom Ihave called substituted ester groups.

For a detailed description of estersils prepared from primary andsecondary unsubstituted monohydric alcohols, reference is made to thecopending U. S. application of Ralph K. Iler, Serial No. 171,759, filedJuly 1, 1950, now abandoned, or to Iler United States Patent 2,657,149,issued October 27, 1953, as a continuation in part of said applicationSerial No. 171,759, in which estersils of that class are claimed.

The substrate The materials used to form the skeleton or internalstructure, the so-called substrate, of the products of my invention aresolid inorganic siliceous materials. They contain substantially nochemically bound organic groups.

They have reactive surfaces which I believe to result from surfacesilanol (SiOH) groups.

The substrate materials can be mineral or synthetic in origin. They canbe amorphous silica. They can be water-insoluble metal silicates. Theycan be water-insoluble metal silicates coated with amorphous silica.

For the purposes of this invention the substrate particles should havean average diameter greater than about 1 millimicron. Substrateparticles in which the ultimate units have diameters of at least 5millimicrons but less than 100 millimicrons are preferred. Anotherpreferred type of substrate particles are supercolloidal aggregates orpulverulent solids.

' It is further preferred that the inorganic siliceous solids used areporous, that is, they have exposed surfaces in the interior of theparticle which are connected to the exterior so that liquids and gasescan penetrate the pores 2 and reach the exposed surfaces of the porewalls. In other words, the solid forms a three-dimensional network orwebwork through which' the pores or voids or interstices extend as alabyrinth of passages or open spaces.

Especially preferred are porous inorganic siliceous solids havingaverage pore diameter of at least four millimicrons. The large poresalford easy access for glycol molecules in the subsequent esterificationto give the products of the invention.

- The substrate particles have largesurface areas in relation to theirmass. 7 The term used herein and the one normally so used in the art toexpress the relationship of surface area to mass is specific surfaceareal Numcrically, specific surface area will be expressed in squaremeters per gram (m. /g.).

According to the present invention, the substrate particles'have anaverage specific surface area of at least 1 square meter per gram andpreferably the average specific surface area is at least 25 mF/g. In thecase of precipitated amorphous silica, a preferred material, there is anoptimum range of about 200 to 1400 m. /g., based on the fact that inthis range the supercolloidal particles or aggregates can be obtained ina dry state without bringing about a considerable collapse of the porousstructure by replacing the water with a water-miscible organic solventsuch as acetone and then drying. This powder is especially suitable forsubsequent esterification. It is, of course, possible to produce veryvoluminous aerogels by processes of the prior art, having surface areasof from 200 to 900 mF/g. Such highly porous forms of silica can besurface-esterified by the process of this invention.

Specific surface area, as referred to herein, is determined by theaccepted nitrogen adsorption method described in an article A New Methodfor Measuring the Surface Areas of Finely Divided Materials and forDetermining the Size of Particles by P. H. Emmett in Symposium on i isillustrated in the examples.

New Methods for Particle Size Determination in Sub- Sieve Rangepublished by the American Society For Testing Materials, March, 1951,page 95. The value of 0.162 square millimicron for the area covered byone surface adsorbed nitrogen molecule is used in calculating thespecific surface areas.

Pore diameter values are obtained by first determining pore volume fromnitrogen adsorption isotherms as described by Holmes and Emmett inJournal of Physical and Colloid Chemistry 51, 1262 (1947). From thevolume figure, the diameters are obtained by simple geometry assumingcylindrical pore structure.

Determinations of gross particle size and shape of substrate materialare suitably made by a number of standard methods whose choice for usein a particular case depends upon the approximate size and shape of theparticles and the degree of accuracy desired. Thus, for coarsematerials, the dimensions of individual particles or coherent aggregatescan be determined with the unaided eye and ruler or calibers. For morefinely powdered material, the light microscope is used with a calibratedscale. For materials having a particle size in the range of from 2 or 3microns down to 5 millimicrons, the electron microscope is used.Particle size determination using an electron microscope is described indetail by J.'H. L. Watson in Analytical Chemistry 20, 576 (1948).

While various inorganic siliceous solids having the aforementionedproperties can be used as substrate materials in preparation of theproducts of my invention, precipitated amorphous silica is particularlypreferred. Such silica is characterized by X-rays as lacking crystallinestructure.

The preparation of several suitable amorphous silicas For a detaileddiscussion 3 f sources of amoiphous silica for use in preparing:stersils of primary and secondary alcohols, reference ihould be had tothe copending U. S. application of {alph K. Iler, Serial No. 171,759,filed July 1, 19.50, w abandoned. V

Instead of silica, Water-insoluble metal silicates can 3e used as thesubstrate. Such metal silicates can be Jrepared, as is well known in theprior art, by treatment Jf' silicas with metal salts or hydrousmetal'oxid'es exe :luding' those containing only alkali. metal ions.Such netal' silicates can be prepared so as to have a large iumber ofsilanol (-SiOI-I) groups on the surface of the particle. Thus, metalsilicates having a largeproportion of metal ions on the surface may beactivated for esterifization' by washing With acids'to remove a portionof the metal ion and leave surface silanol groups.

Crystalline metal-silicates occurring in nature can also be used.However, the proportion of silanol groups on most minerals is very smallsince the surfaces also contain metal hydroxy groups, silicon oxygengroups and adsorbed metal ions. Therefore, before esterification it isnecessary to introduce silanol groups on the surface. Loosely adsorbedmetal ions may be exchanged for hydrogen ions by washing the diluteacids or by treatment with ion exchange resins. In some cases, morevigorous treatment, such as reaction with acids at low pH and often atelevated temperatures are required to give a material which will containa suflicient number of silanol groups in the surface to yield anorganophilic product on esterification.

Alternatively or additionally, silanol groups can be introduced on thesurface of metal silicates by coating them with a layer of amorphoussilica. This is accomplished by treating, say, sodium silicate with anacid in the presence of the mineral silicate particles under suchconditions that the silica formed will deposit as a coating on themineral particle.

Mineral crystalline silicates which can be used in preparing thesubstrate particles are as follows: the asbestos minerals, such aschrysotile asbestos and serpentine (hydrous magnesium silicate) andamphiboles such as crocidolite asbestos (a sodium magnesium ironsilicate),

amosite an iron silicate), tremolite (a calcium mag-Z nesium silicate),and anthothyllite (a magnesium iron silicate); clay materials, such ashalloysite (an aluminum silicate), attapulgite (a magnesium aluminumsilicate), hectorite (a magnesium lithium silicate), nontronite(magnesium aluminum iron silicate); the kaolins, such as kaolinite,nacrite and dickite' (aluminum silicate); and bentonites, suchasbeidillite, saponite and montmorillonite (magnesium aluminum ironsilicates); and micaceous minerals, such as phlogopite (a potassiummagnesium aluminum silicate), muscovite (a potassium aluminum silicate),biotite; (a potassium iron'aluminum silicate) and; vermiculite (ahydrous magnesium iron aluminum silicate).

The csterifying agent methylene glycol, dodecamethylene glycol,tridecameth-u ylene glycol, tetradecamethylene glycol,pentadecamethylene glycol, hexadecamethylene glycol, heptadecamethyleneglycol, octadecamethylene glycol, 4,5-octanediol, 2-,4-hexanediol and2,4-actanediol.

Technically, there is no upper limit to the number of carbon atoms whichmay be present in the esterifying agent. As a practical matter, however,the group of glycols having from 2 to 18 carbon atoms include themajority of common glycols and offer a selection of molecule sizes whichshould be adequate for any purpose.

Glycols containing from 2 to 6 carbon atoms are preferred. They are themost economical to use and'yield products having a low ratio of organicmatter tojsilica.

The esterifying agent need not be a single glycol. Mixtures of glycolscan be used; Thus,when a variety of surface properties is desired, amixture. of glycols can be employed as the esterifying agent.

Esterification The siliceous substrate to be reacted with both of thehydroxyl groups of the glycol should contain surface silanol groups.Pure amorphous silica which has been in contact with moisture has such asurface; The surface must not be covered with other materials whiclrblock access to the silanol group. Metal ions on the surface of metalsilicates must be exchanged for hydrogen atoms. This'can be done bytreatment with a hydrogen form of acation exchange resin or by treatmentwith an acid as mentioned heretofore. Alternatively, the particles canbe coated with a thin layer of silica. The external-surface can then bereacted with'glycol.

The inorganic siliceousrsolid is preferably freed of extraneous materialbefore esterification, and the pH- is adjusted to avoid strong acids oralkali in the reaction. The pH is preferablyS to 8.

The amount of water present in thereacting mass during theesterification step has an important; bearing on the degree ofesterification that will be obtained. Thus, since the esterificationprocess is an equilibrium reaction; it is ordinarily desirable, to keepthe water content as low as'possible during the course of the reaction.

In order to esterify'sufficiently to obtain a high proportion. ofsubstituted ester groups on the surface of the siliceous particles, thewater in the liquid phase of. the

. system should not exceed about 5% by weight of-that phase. For maximumesterification, the water content must be kept below about 1.5%. Asalready mentioned, it is desirable to keep the water content as low aspossible. Because of the hindering effect of water. on the .esterification, if the siliceous solid. to be esterified is wet,.the

' free water must be removed. either before the solid is put into theglycol, or alternatively itmay be removed by distillation after mixingwith the glycol.

Simple air drying at temperatures of from to C. will remove most of thefree water. Drying may be hastened by the application of vacuum. Formany types of siliceous solids, however, air drying is not satisfactorybecause they tend to shrink to hard, compact'masses upon drying fromwater.

Water can suitably be removed from a wet siliceous solid beforeesterification by displacing the water in' the wet mass with a polarorganic solvent such as acetone.

The solvent can'later be recovered.

Preferably, water is removed-from wet siliceous solids prior: toesterification by azeotropic distillation; Il-rus; water-Wet cake can bemixed with a polar organic solvent such as methyl ethyl ketoneand themixture distilled until the'system is freed from water. The organicsolvent can then be evaporated to give a dry product for reaction withglycol. p

The ratio of glycol and siliceous material to be used inthe'esterification is important. In order to insure that both hydroxylgroups of the glycol become attached to the silica surface, an excessamount of glyool shouldbe avoided, particularly in those instances wherea glycol having its hydroxy groups separated by more: than: 3 carbonatoms is used.

' It will be. ob'servedthat the glycol should be dilute tween the silicaand the esterifying agent.

with a hydrocarbon solvent such as, for instance, benzene, toluene orxylene. The presence of the hydrocarbon solvent prevents local excessesof the glycol from gathering at the silica surface and helps to orientthe hydroxyl groups toward the silica surface dueto 'the relativelygreater afiinity of the hydrocarbon solvent for the hydrocarbon portionof the glycol.

In instances where the glycols used have hydroxyl groups on adjacentcarbon atoms or on carbon atoms separated by a single carbon and havelong hydrocarbon chains attached to these carbon atoms, it is felt thatthe glycols are'rnore readily oriented in such a 'way that both hydroxygroups can be directed toward the surface. Consequently, in theseinstances, the ratio of glycol to silica may be incre'asedsomewhat;

The surface esterification can be effected by refluxing the mixture ofthe silica, glycol and the hydrocarbon solvent together for a suitablelength of time, for example, upwards of 2 hours, or by autoclaving.

The extent of the reaction is fixed more by the temperature than by thetime, that is, at a suitable temperature the esterification reactionproceeds quite rapidly up to a certain point which is characteristic ofthe temperature and of the glycol and thereafter proceeds slowly.

The minimum reaction time and temperature in order to obtain any givenextent of reaction varies with'the glycol used. While it is difficult toset forth in great detail the relationship between the temperaturerequired for any given extent of reaction and the structure of theglycol, one skilled in the art may learn from the data the generalprinciples involved and conclude what conditions should be used foranother glycol.

The temperatures substantially below about 100 C. are not suitable inmost instances. Glycol may be adsorbed on the siliceous surface at suchtemperatures but true esterification is not obtained.

The esterified temperature should not exceed the thermal decompositionpoint of the glycol while in the presence of siliceous solids. .Norshould it exceed thepoint of thermal stability of the esterifiedsiliceous materials.

Preferably, the heating is not prolonged any more than is required toachieve esterification equilibrium.

Whether the reaction is effected at atmospheric pressure at the refluxtemperature of the solution or under autoclave conditions will largelydepend on the boiling point of the solvent used; that is, whether theboiling point is high enough to effect substantial reaction be-Occasionally, it is desirable to deposit a mono layer of the glycoluniformly over the silica surface by stirring the latter with a solutionof the glycol in a low boiling, inert solvent such as ether or acetone,and then evaporating the solvent while maintaining constant agitation.Complete reaction is then effected by heating the dry, coated product toa temperature sufficiently high to cause removal of water.

After completion of the esterification, the product estersils can beremoved from the solvent and any unreacted glycol by conventionalmethods. Thus, the separation can be made by filtration in thoseinstances where the estersils consist of particles of supercolloidalsize, the estersils being retained on ordinary filter media.

'Alternatively, the glycol can be vaporized by applying vacuum to thereaction vessel. If the glycol is one which will distill at atmosphericpressure without decomposition, simple distillation can be used. In thecase of higher glycols which are not readily distilled, except undervery high vacuum, the glycol can be extracted from the product with alow boiling solvent such as, for instance, methyl ethyl ketone,chloroform or ether.

ders or sometimes lumps or cakes which are pulverable under the pressureof the finger or by a light rubbing action. The esterified'inorganicsiliceous solids are generally exceedingly fine, light,fiufiy,voluminous powders.

The esterification reaction does not substantially change the structureof the inorganic siliceous solid or substrate which Was esterified. Inother words, the internal structure of the cstersil, the structure towhich the ORO-- groups are chemically bound, has substantially the sameparticle size, surface area and other characteristics describedpreviously in the discussionof the substrate material. The 'estersilsofthe inventionare in a colloidal or supercolloidal'state of subdivision.

The products of the invention areorganophilic. -In those instances wherea glycol having more than six carbon atoms is employed as theesterifying' agent in accordance with this invention the product ishydrophobic.

By the term orga'no'philic I mean that when apinch of estersil is shakenin a two-phase liquid system of water and n-butanol in a test tube theproduct will wet into the n-butanol phase in preference to thewater-phase.

In the case of the preferred glycols, it is possible to force more hair100 glycol molecules, say 200 or more, to react per 100 squaremillimicrons of surface area of the siliceous subtrate by using severereaction conditions, care being take not to decompose the glycol or theresulting substituted ester group.

The number of ester groups for 100 square millimicrons of siliceoussubstrate surface is calculated from the expression: 1

10 50,2003 q Surface arean where C is the weight of the carbon in gramsattached to 100 grams of substrate; n is the number of carbon atoms inORO- groups; Sn is the specific surface area in r'n.2/ g. of thesubstrate as determined by nitrogen adsorption.

Where the sample to be analyzed is one in which the type of glycol isunknown, the sample can be decomposed with an acid and the glycol'can berecovered and identified. The specific surface area of the substrate canbe determined byfirstburning off the ester groups, as for example, byslowly heating the estersil in a stream of oxygen up to 500 C. andholding it at that temperature for a period of about three hours andthen rehydrating the surface of the particles by exposure to relativehumidity at room temperature for several hours and finally determiningthe surface area of the remaining solid by nitrogen adsorption method. j

The specific hydroxylated surface areas of silicas having surfacesilanol groups may be calculated by measuring the amount of methyl reddye which will absorb on such surfaces. A description of such a methodof determining hydroxylated surface areas has been published by I.Shapiro and I. M. Kolthofi? in the Journal of the American ChemicalSociety 72, 776 (1950).

The methyl red adsorption test is carried out by agitating a suspensionof a few tenths of a gram of a dried silica or esterified silica sampleto -be tested in 25 ml. of an anhydrous benzene solution containing 0.6to 0.7 gram of the acid form of methyl redp-dimethylaminoazobenzen-o-carboxylic acid,

per liter. No more than about 0.7 gram of the sample should be used inthe test. With voluminous samples less than 0.7 gram, say, for instance,0.4 gram, should be used to avoid getting a mixture too thick to handle.

The amount of sample used in the methyl red adsorption test shouldprovide, as near as possible, a total hydroxylated surface area of 10 m?in the test. The test mixture is agitated for a period of about twohours at a temperature of about 25 C. to reach equilibrium conditions.An equilibrium concentration of 400 milligrams of dye per liter insuressaturation adsorption.

The decrease in dye concentration in the benzene sograms dye adsorbedXl'lbX 1'0- Avogadros N0.

rams silica employedXmolecular weight of methyl red I lhdl'fi thecovering .power of each adsorbed methyl red iolecule is approximately1.1.6 square inill imicrons. I

When the surfacesof the siliceous materials are-esterited, the methylred dye will not be .adsorbed on the sterified portions of the surface;that is, on the por ions of the surfacej not' covered by; silanolgroups.

Ionsequently, measurement of the adsorption of methyl ed dye before andafter the siliceous material has been ubjected to a process of myinventionshows a'decrease vhich is proportional to the decrease inexposed specific iydroxylated surface area.

Since the amount of dye adsorbed by the sample is neasured bydifference, the probable error, percentagevise, increases as the amountof adsorbed dye decreases. Thus, for specific hydroxylated surface areasof 100 n. /g., variationsof as much as 5 m. /g. are possible.

For samples which have a specific surface area of about 100 mF/g. asdetermined by nitrogen adsorption, and which adsorb very little dye,- avaluefor the hydroxylated surface area of less than 5 mF/g. isconsidered to be essentially zero.

In the products of the invention the --ORO-- groups are chemically boundto the substrate. The products should not be. confused with compositionsin which a glycol is merely physically adsorbed on the surface of thesiliceous solid. Adsorbed. glycols can be removed by heating thematerial at relatively low temperature, for example, 150 C. under highvacuum, say, millimeters of mercuryfor aperiod of one hour. In

contrast, the products of my invention are stable un- I der suchtreatment. Neither can theester groups be removed by washing with hotmethyl ethyl ketone or similar solvents or by prolonged extraction in aSoxhlet extractor. In case of ordinary physical adsorption the alcoholis displaced by such treatment.

The products of the. inveniton find utility in those fields in whichorganophilic and hydrophobic materials are used. The products areparticularly useful as grease thickeners and as fillers for. plasticsand e'lastomers such as, for instance, natural rubberyG-R-S rubberandsilicone rubber.

The invention will be; better. understood by reference to the followingillustrative example:

Example 1 A silica powder isobtainedby the gelationof a com: merciallyavailable v% silica sol consisting of 17 millimicron colloidal particlesand known as Ludox" Colloidal Silica andby drying the gel at atemperature of 110 C. for a period'of twenty-four hours at a pH of about4.5. Products 'of this character are described and claimed in. thecopending application of Max F. Bechtold and Omar E. Snyder,v Serial No.256,142, filed November 13, 1951.

The dried material, which is-in'the' formof coherent aggregates ofdense, ultimate units of amorphous silica, is dispersed to av freefiowing powder by the use of a micro pulverizer.

A portion ofthe aforementioned powder is heated in a muffie. furnace inthe presence of air for a period of two hours at a temperature of 625 C.in accordance with the invention described and claimed in the copendingU. S. application of Warren K. Lowen, Serial No. 261,139, filed Decemberll, 1 951. .Thehat treatment activates the siliceous surface towards:reaction withhydroxy groups.

Ten: parts ofithe surface-activated silica: is slurried into to effect,surface 'esterific'ation.

. test.

a solution consisting of -0.5 part by "weight of hexameth-ylene glycoland, about 260 parts by weight of xylene. The resulting mixture isheated at a temperatu'reof about 135 C." for a periodof 3 hours in orderThe slurry is allowed to cool slowly and'then'filtered. Thesurface-esterified silica is collected, washed with acetone, and vacuumdried at a temperature ofr1Q2" C. for a periodof 16 hours.

The driedproduct is organophilic; The pronounced compatibility of theproduct withorganic solvents is evidence that the surface of the.estersil is substantially non-polar. In other words, both of thehydroxyl groups of hexamethylene. glycolhave reacted with thesilicasurface. The fact that reaction between both OH groups of the glycol andthe silica surface has occurred is'furth'er substantiated by a polarsurface area measurement of the product utilizing the methyl red dyeadsorption The hydroxylated surface areao'f the productas determined bythe methyl reddye testis 15 m. g. The total specific surface area asmeasured by nitrogen adsorption is about 175 m. /g.

1 A solid consisting essentially of substrate particles of inorganicsiliceous material having 'an average specific surface area of from 1 to900 square meters per gram, having anaverage particle diameter greaterthan about 1 millimicron, and having chemically bound to thesiliconatoms on the surface of said particles at least 100 ORO' groupsper 100 square rnilli'microns of surface area of the siliceous material,where R is a divalent hydrocarbon radical having from 2 to 18 carbonatoms in which each of the carbon atoms attached to oxygen is alsoattached to at least one hydrogen atom.

2. A powder consisting essentially of substrate particles of amorphoussilica having an average specific surface area of from 25 to 900 squaremeters per gram, having an average particle diameter greater than aboutl millimicron, andhaving-chemically bound to the silicon atoms -onthesurface of said particles at least 100 7 in which each of the carbonatoms attached to oxygen is also'attached to at least one hydrogen atom.

3. A powder consisting essentially of substrate parti cles of amorphoussilica in a supercolloidal state of subdivision having anaveragespecific surface area of froml to 900'squa1'e meters'per gram, having anaverage pore diameter of at least 4 millimicrons, and having chemicallybound to the silicon atoms on the surface of saidparticles at least--ORO- groups per 100 square millimicrons of surface area of thesiliceous material, where R is a divalent hydrocarbon radical havingfrom 2 to 18 carbon atoms in which each of the carbon atoms attachedtooxygen is also attached to at least one hydrogen atom. 4. A powderconsisting essentially of substrate particles of amorphoussilica in. asupercolloidal state of subdivision having anavcrage specific surfacearea of from 25 to 900 square meters per gram, having an average porediameter of at; lcastl 4' millimicrons, and having chemically bound'tothefs'ilicon. atoms on the'surface of said par ticles' at least 100ORO'- groups per 100 squaremillimicrons of surface areaof the siliceousmaterial, where R is a divalent hydrocarbon radical having from'2 to 18carbon atom'sin which each of. the carbon atoms attached to. oxygen'isalso attached to at least one hydrogen atom. 5. A process whichcomprises the step of chemically reacting in a hydrocarbon which is asolvent for the glycol, a glycol of, the formula HOROH in which R is adivalent hydrocarbon radical having from 2 to 18 carbon atoms, whereineach. of the carbon: atoms attached to oxygen. is alsoattachedto atleast one hydrogen, in a hydrocarbon which is a solvent for the glycol,with an inorganic siliceous material having an average specific surfacearea of from 1 to 900 square meters per gram, having an average particlediameter greater than about 1 millimicron, and having a reactive surfacecontaining groups selected from the class consisting of silanol andheat-activated silicon-oxygen groups, while maintaining the watercontent of the system below about per cent by weight of the glycol inthe system and the temperature in the range from 100 C. to the thermaldecomposition temperature of the glycol.

6. A process which comprises the step of chemically reacting at atemperature of at least 100 C. and in an aromatic hydrocarbon solvent aglycol of the formula HOROH in which R is a divalent hydrocarbon radicalhaving from 2 to 18 carbon atoms, wherein each of the carbon atomsattached to oxygen is also attached to at least one hydrogen, with aninorganic siliceous material in a supercolloidal state of subdivision,having an average specific surface area of from 1 to 900 square metersper gram,having an average particle diameter greater than about 1millimicron, and having a reactive surface containing groups selectedfrom the class consisting of silanol and heat-activated silicon-oxygengroups, while maintaining the water content of the system below about 5per cent by weight of the glycol in the system and the temperature inthe range from 100 C. to the thermal decomposition temperature of theglycol.

7. A process which comprises the step of chemically reacting in thepresence of an aromatic hydrocarbon solvent a glycol of the formulaHOROH in which R is a divalent hydrocarbon radical having from 2 to 18carbon atoms, wherein each carbon atom attached to oxygen is alsoattached to at least one hydrogen, with an inorganic siliceous materialin a supercolloidal state of subdivision, having an average specificsurface area of from 1 to 900 square meters per gram having an averageparticle diameter greater than about 1 millimicron, and having areactive surface containing groups selected from the class consisting ofsilanol and heat-activated silicon-oxygen groups, While maintaining thewater content of the sys tem below about 5% by weight of the glycol inthe system and the temperature in the range from C. to the thermaldecomposition temperature of the glycol until at least 100 ORO- groupsper 100 square millimicrons of surface area of said inorganic siliceoussolid are chemically bound thereto.

References Cited imthe file of this patent UNITED STATES PATENTS2,395,880 Kirk Mar. 5, 1946 2,438,379 Archibald et a1 Mar. 23, 19482,454,941 Pierce et al Nov. 30, 1948

1. SOLID CONSISTING ESSENTIALLY OF SUBSTRATE PARTICLES OF INORGANICSILICEOUS MATERIAL HAVING AN AVERAGE SPECIFIC SURFACE AREA OF FROM 1 TO900 SQUARE METERS PER GRAM, HAVING AN AVERAGE PARTICLE DIAMETER GREATERTHAN ABOUT 1 MILLIMICRON, AND HAVING CHEMICALLY BOUND TO THE SILICONATOMS ON THE SURFACE OF SAID PARTICLES AT LEAST 100 -ORO- GROUPS PER 100SQUARE MILLIMICRONS OF SURFACE AREA OF THE SILICEOUS MATERIAL, WHERE RIS A DIVALENT HYDROCARBON RADICAL HAVING FROM 2 TO 18 CARBON ATOMS INWHICH EACH OF THE CARBON ATOMS ATTACHED TO OXYGEN IS ALSO ATTACHED TO ATLEAST ONE HYDROGEN ATOM.
 5. A PROCESS WHICH COMPRISES THE STEP OFCHEMICALLY REACTING IN A HYDROCARBON WHICH IS A SOLVENT FOR THE GLYCOL,A GLYCOL OF THE FORMULA HOROH IN WHICH R IS A DIVALENT HYDROCARBONRADICAL HAVING FROM 2 TO 18 CARBON ATOMS, WHEREIN EACH OF THE CARBONATOMS ATTACHED TO OXYGEN IS ALSO ATTACHED TO LEAST ONE HYDROGEN, IN AHYDROCARBON WHICH IS A SOLVENT FOR THE GLYCOL, WITH AN INORGANICSILICEOUS MATERIAL HAVING AN AVERAGE SPECIFIC SURFACE AREA OF FROM 1 TO900 SQUARE METERS PER GRAM, HAVING AN AVERAGE PARTICLE DIAMETER GREATERTHAN ABOUT 1 MILLIMICRON, AND HAVING A REACTIVE SURFACE CONTAININGGROUPS SELECTED FROM THE CLASS CONSISTING OF SILANOL AND HEAT-ACTIVATEDSILICON-OXYGEN GROUPS, WHILE MAINTAINING THE WATER CONTENT OF THE SYSTEMBELOW ABOUT 5 PER CENT BY WEIGHT OF THE GLYCOL IN THE SYSTEM AND THETEMPERATURE IN THE RANGE FROM 100*C. TO THE THERMAL DECOMPOSITIONTEMPERATURE OF THE GLYCOL.